Loading dock rail shelters form a temporary enclosure between a railroad car and the loading bay of a building. Rail shelters are typically used in conjunction with a dock leveler that forms a bridge between the dock and railcar floors. The shelters prevent rain, snow and ice from accumulating on the floors of the loading bay, railcar, dock leveler and the cargo, and provide a safer environment for loading and unloading operations. Rail shelters can have three or four sides. Three-sided shelters have a top and two side portions that extend over and around the sides of the leveler, and provide a 270 degree seal with the railcar. Large openings remain between the sides of the leveler and the sides of the canopy. Heat, cold, humidity, wind, dust, insects, etc., easily pass through these openings and into the interior of the loading dock, which is of particular concern for refrigerated docks and those handling food products. Four-sided shelters include a bottom portion that extends under the leveler, close the opening along the dock leveler and form a 360 degree seal with the railcar.
Various inflatable rail shelters have been developed and are known in the industry, examples being the Perma Tech 3600 shelter, the Rite-Hite RAIL-DOX shelter, the Fairborn Series 4500 shelter, the Nordock IR-650 shelter and the Super Seal Manufacturing Series R shelter. These rail shelters have a conventional inflatable canopy formed by a series of interconnected air bags. The inner air bag secures to the loading dock wall around the bay opening. When the canopy is inflated by a blower motor, the canopy extends so that its outer air bag seals around the railroad car doorway. Disengaging the blower motor allows the canopy to deflate and retract toward the loading dock building. Elastic bungee cords are often secured to the building to pull the canopy back toward the building wall. A trolley can be cantilevered from the dock wall to support the top of the canopy.
Conventional rail shelters suffer from a variety of problems. One problem is maintaining a required amount of clearance between the deflated shelter and the railcars passing along the railroad tracks. Railroad companies require facilities to be a certain distance from the tracks (i.e., nine feet from the centerline of the tracks) to avoid contacting or interfering with a passing train. When not in use, shelters must comply with this requirement. Bungee cords are commonly used to help retract the inflated canopy and keep it against the building wall. These cords deteriorate, fatigue and break over time, so that they do not effectively hold the entire canopy against the building wall. High winds or gusts of wind can catch a portion of the deflated canopy and blow it toward and into the structure-free zone by the tracks, where it can be struck or snagged by or interfere with a passing train.
Another problem with conventional loading dock rail shelters is that the sides and bottom of the canopy drag along the ground when inflating and deflating. This problem is of particular concern for four-sided canopies with a bottom portion. While inflating and deflating, the floppy canopy hangs down and drags along the ground. The ground along the tracks includes stones, sticks and debris such as broken bottles, crushed cans, boards and nails, etc., that are rough, sharp and jagged, and which can damage the canopy. While bungee cords may reduce the amount of dragging in some situations, they do not eliminate this problem, particularly for four-sided canopies and when the tracks are located further from the building and the canopy must extend a greater distance.
A further problem with conventional loading dock rail shelters is that they do not properly stabilize the canopy when inflated. High winds and gusts of wind can easily push the extended canopy back and forth over rusted, blunt, sharp or jagged components projecting from the surface of a railroad boxcar. Repeated rubbing contact with these surfaces and projections can wear down, tear or otherwise damage the canopy. The blower motor has to constantly run to maintain a proper seal or the damaged canopy has to be replaced. The accumulation of snow or rain on the canopy can also push it down and out of alignment with the railcar doorway, which interferes with boxcar loading and unloading operations.
A still further problem with conventional loading dock rail shelters is they do not properly stabilize the canopy when deflated. Bungee cords have a static or unstretched cord length. This unstretched cord length can be significant in order to allow the canopy to fully extend and seal against a boxcar. The cords provide little or no retraction force when the canopy is close to the dock wall. Individual cords also provide a localized force on separate parts of the canopy. High winds and gusts of wind can catch portions of the floppy deflated canopy and push them back and forth over the rough cinder block surface of the dock wall, building projections, or debris on the ground, which can wear holes in or otherwise damage the canopy.
A still further problem with conventional loading dock rail shelters is maintaining uniform and constant support around the entire perimeter of the shelter. Trollies support the top of the canopy but not the bottom of a four-sided canopy, which is free to hang down and drag along the ground. Bunge cords provide spaced and varying amounts of pullback force. These elastic cords pull excessively on the canopy fabric and hemmed seams when the canopy is fully extended, which can tear the fabric or otherwise damage the canopy. Bungee cords are not typically used on the bottom of a four-sided canopy because cords secured under the canopy pull the bottom and side portions down and into contact with the ground.
A still further problem with conventional loading dock rail shelters is they do not stably accommodate varying railcar configurations. Railcars come in a variety of widths and heights. Wider railcars extend out from the tracks more than narrower railcars. Canopies must extend a greater distance from the building to engage a narrower railcar, and must be able to extend a lesser distance to engage a wider railcar. Taller railcars have taller doorways, and the car floor can be higher above the tracks. Conventional inflatable rail shelters do not provide proper and stable sealing engagement with a variety of different boxcar configurations. For example, the canopy can sag when engaging a wider railcar because it is not fully inflated. Bungee cords can aggravate this problem because the amount of their pullback force varies depending on the width of the boxcar and height of its doorway.
The present invention is intended to solve these and other problems.